iio: st-accel: add support for lis3de

This commit add support for STMicroelectronics lis3de accelerometer.
Datasheet for this device can be found here:

https://www.st.com/resource/en/datasheet/lis3de.pdf



Signed-off-by: Heiko Stuebner <heiko.stuebner@bq.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>